This invention is an outgrowth of the development of molded polyurethane foam-backed fabrics (and, particularly carpets) which are sufficiently stiff upon demolding to retain their shape and yet are not so stiff that they crack when bent. The process for making such foamed-backed fabrics involves the application of a heat curable froth or foamable mixture of polyurethane reaction components to the back of a fabric. The polyurethane is then cured, normally under heat, to a tack-free, gelled state. The fabric is then cut into sized pieces and molded to the desired shape.
The general drawback to this process is the difficulty in formulation a system which can undergo the above mentioned steps in an industrial setting. Until now, it has not been possible to produce a tack-free, gelled foam backing which could be stored for long periods of time, be cut into a desired sized piece when needed, and molded in a reasonably short period of time into a molded part which will retain its shape while at the same time not being so stiff that it will crack if bent.
The general method of applying foam to a fabric substrate and subsequently molding the laminate into a desired shape is known e.g. U.S. Pat. Nos. 3,175,936; 3,046,177; 3,440,307; 3,772,224; 3,849,156 and 3,175,936. None of these methods, however, permits the foam-backed fabric to be stored for prolonged periods and then be hot molded at a much later time into excellent contoured laminates.
In U.S. Pat. No. 3,860,537, a foam which is storable in a roll is produced and is capable of being molded at a later time. The method requires the use of a significant quantity of an ethylenically unsaturated polyester together with an ethylenically unsaturated monomer copolymerizable with the polyester. The shortcoming of the process is that the curing/molding step requires molding times of 30-35 minutes (note Examples 1 and 10) which is an economically unacceptably long time. The patent also fails to suggest applying the foamable reaction mixture to the back of a fabric, or in fact to any substrate.
The present invention utilizes a hydroxy functional acrylate and a free radical initiator as a means of overcoming the lengthy mold time. The use of hydroxy functional acrylates is not new to the polyurethane art. For example, there are the polymer polyols e.g. U.S. pat. Nos. 3,383,351; 3,652,639; 3,523,093 and 3,576,706. There are a number of coating applications described in U.S. Pat. Nos. 3,975,457; 3,919,351; 3,989,609. There are also patents such as U.S. Pat. No. 3,954,584 directed to a photo polymerizable vinyl urethane composition and U.S. Pat. No. 4,052,282 directed to a photocurable bandage. However, as far as Applicant is aware, there is no prior art directed to the specific application of producing a curable and moldable polyurethane foam which has been applied to a fabric substrate.